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mthomassen | 5 years ago

I assume you're using ZFS filesystem for the transparant compression, what's your opninion/experience on using ZFS on cloud storage? I mean; the EBS disks are already redundantly stored by AWS and the COW mechanism could lead to a lot of write amplification; negatively impacting the network attached storage?

(I don't use EBS in my day job, but Azure's disk offering don't really offer adequate perforamance when used with any filesystem other then EXT4 in my experience)

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krnaveen14|5 years ago

There is a small write amplification due to pg page size being 8KB and ZFS recordsize being 128KB, but considering the Bulk write nature there is not much impact. Also max IO size of EBS is 256KB which helps us to optimally utilise available IOPS even if there is write amplification. Reducing the ZFS recordsize significantly reduces compression ratio so we kept as it is. If it's an OLTP application, reducing the recordsize will improve latency but for these bulk operations, it's the most suitable.

I haven't used Azure, but based on my raw benchmark and real time usage, I would say type of FileSystem doesn't affect performance of EBS Volumes. Our peak IO usage is 1200 IOPS and 20 MB/s. I would say similar RDS configuration would have x4 - x10 write amplification due to data being not compressed.